More stringent requirements are often applied to machine washed dishes than are applied to hand washed dishes. For instance, a dish which is at first glance completely clean of food residues is not deemed to be perfect if it still exhibits discoloration after automatic dishwashing which results for example from the deposition of vegetable dyes on the surface of the dish.
To achieve spotless dishes, bleaching agents are used in automatic dishwashing agents. To activate these bleaching agents and in order to achieve an improved bleaching action at temperatures of 60° C. and below, automatic dishwashing agents generally additionally contain bleach activators or bleach catalysts, bleach catalysts in particular having proven particularly effective.
Limits often apply to the use of these bleaching agents due to incompatibility with other ingredients with a washing or cleaning action, such as for example enzymes, or due to stability problems during the storage of washing and cleaning agents containing bleaching agents. This also applies in particular to liquid washing or cleaning agents.
One technical option for enhancing the cleaning performance of automatic dishwashing agents, in particular bleaching agent-free automatic dishwashing agents, is to increase the alkalinity of these agents. However, while on the one hand the cleaning performance of automatic dishwashing agents increases at higher levels of alkalinity, strongly alkaline cleaning products on the other hand also cause damage to the silicate structure of glasses and may trigger severe irritation on skin contact.
Alkali metal phosphates have proved to be particularly effective builders for increasing alkalinity, for which reason they form the main ingredient of the majority of commercially obtainable automatic dishwashing agents.
While phosphates are very highly regarded in terms of their advantageous action as a component of automatic dishwashing agents, their use is not entirely unproblematic from an environmental protection standpoint since a significant proportion of the phosphate passes with domestic wastewater into bodies of water and, especially in standing bodies of water (lakes, dams), plays a considerable part in their eutrophication or overfertilization. As a consequence of this phenomenon, the use of pentasodium triphosphate in textile washing agents has been considerably reduced by statutory regulations in quite a number of countries, for example the USA, Canada, Italy, Sweden, Norway, and has been entirely prohibited in Switzerland. In Germany, since 1984, the permitted maximum content of this builder in washing agents has been 20%.
From the user's standpoint and with regard to sustainable product development it is thus desirable to limit not only the alkalinity but also the phosphate content of automatic dishwashing agents.
The object underlying the present application was accordingly to provide cleaning agents for cleaning dishes which, in comparison with conventional agents for cleaning dishes, is distinguished by improved cleaning performance even in low temperature cleaning cycles or in cleaning cycles with low water consumption. In particular, the intention was for the agent for cleaning dishes, despite containing neither phosphate nor bleaching agent, to be distinguished by good cleaning performance, it being preferable to obtain improved cleaning performance, for example towards bleachable soiling, without simultaneously bringing about elevated damage to glass or ceramic surfaces. Bleachable soiling here includes, for example, soiling by tea or plant dyes for example from vegetables or fruit.
It has surprisingly been found that the above-stated object may be achieved by using specific polymers in a citrate-based base formulation. Other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.